Generally, an air bag device for the passenger seat is attached inside of an instrument panel. Conventional attaching mechanisms for air bag device are disclosed in JP-A-2001-39254 and JP-A-2001-47959, for example.
FIG. 16 is a schematic view illustrating an example of conventional instrument panel (indicated by reference number 1). FIG. 17 illustrates an air bag device 8 attached inside the instrument panel 1. The instrument panel is made of resin and formed with an air bag door 10 facing the air bag device 8. The rear side of the instrument panel 1 is formed with a plurality of grooves defining the air bag door 10. As shown in FIG. 16, the grooves 11 include three grooves 11a-11c extending longitudinally of the instrument panel 1 and two grooves 11d, 11e extending perpendicularly to the three longitudinal grooves. The portions formed with the grooves are weaker than the other portions of the instrument panel 1. With such an arrangement, when the air bag (not shown) of the air bag device 8 inflates, the portions formed with the grooves 11 are broken due to the pressure by the air bag. As a result, as shown by the phantom lines in FIG. 17, the air bag door 10 is opened and the air bag comes out of the instrument panel 1.
It is desirable that the air bag door 10 is designed to be prevented from flying into pieces when the air bag door 10 opens. To achieve this, the air bag door 10 is supported by a retainer 80, for example. The retainer 80 is made of a bendable metal plate, and includes an end attached to the air bag device 8. The other end of the retainer 80 is fixed to a rib 13 formed at the rear side of the air bag door 10. Due to this structure, the air bag door 10 is prevented from flying into pieces by the retainer 80 when the air bag door 10 opens.
The instrument panel 1 may be molded from resin material utilizing a molding apparatus B as shown in FIG. 18. The molding apparatus B includes an upper portion 7A, a lower portion 7B, and a plurality of grooving blades 39. The upper portion 7A and the lower portion 7B form a cavity 70 for molding the instrument panel 1. Each grooving blade includes a tip end inserted into the cavity 70 for forming the break grooves 11 at the instrument panel 1. Though it is not shown in FIG. 18, the grooving blade 39 is a rectangular plate. The base ends of the grooving blades 39 are connected to each other.
After the instrument panel 1 is molded in the cavity 70, the upper portion 7A and the lower portion 7B are separated. (JP-A-11-34124 discloses an example of an apparatus for reciprocally moving a mold for resin molding within a predetermined area.) Then, the instrument panel 1 is taken out of the mold.
However, in the prior art, as described below, the instrument panel may not be taken out properly from the mold.
When the instrument panel 1 is taken out from the lower portion 7B, the air bag door 10 tends to remain in the mold more often than the other portions. One cause of this is the ribs 13 formed at the air bag door 10. As the ribs 13 increase the contacting area of the air bag door 10 and the lower portion 7B, the air bag door 10 is not easily separated from the lower portion 7B. If the instrument panel 1 is forcibly pulled to be separated from the lower portion 7B when the air bag door 10 intimately contacts with the lower portion 7B, the weak portions formed with the break groove 11 may be bent or damaged. Further, the bent break groove 11 may be whitened.